Category Archives: 2.1 and 2.2 Structure and bonding

Polymer structure and intermolecular forces

LD and HD poly(ethene) The properties of polymers depend on what they are made from and the conditions under which they are made. For example, low density (LDPE) and high density (HDPE) poly(ethene) are produced using different catalysts and reaction conditions. LDPE HDPE branches on polymer molecules many few relative strength weak strong maximum usable temperature 85 ºC 120 ºC HDPE is more suited for

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Simple covalent molecules

Remember: Covalent bonds form between non-metal atoms. Each covalent represents a shared pair of electrons. Covalent bonds are very strong. There are two types of covalently bound molecule: simple molecules and giant covalent macromolecules (click here). Simple covalent molecules Simple molecular substances consist of molecules in which the atoms are joined by strong covalent bonds. Examples include the covalently bonded

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Metallic structure and bonding

Metals form giant structures containing free electrons, making them good conductors of heat and electricity. Structure and properties Metals conduct heat and electricity because of the delocalised electrons in their structures. Conduction depends on the ability of electrons to move throughout the metal. The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped. The strength

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Ionic compounds

Structure Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces in all directions between oppositely charged ions. Examples of such crystals are the alkali metal halides (e.g. potassium chloride, sodium fluoride, sodium chloride) The exact arrangement of ions in an ionic lattice varies according to the size of the ions in the solid. Example NaCl Each Na+

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Giant covalent macromolecules

Remember: Covalent bonds form between non-metal atoms. Each covalent represents a shared pair of electrons. Covalent bonds are very strong. There are two types of covalently bound molecule: simple molecules (click here) and giant covalent macromolecules.   Carbon allotropes: graphite, diamond, amorphous carbon (soot, charcoal) and fullerenes are all examples of carbon allotropes. Allotropes are forms of an element that

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Atomic structure and bonding

Definition of compound: Compounds are substances in which atoms of two or more elements are chemically combined. Quick reminder: the differences between atoms, elements, ions, compounds and mixtures (click here). Formation of a chemical bond between atoms: Chemical bonding involves either transferring or sharing electrons contained in the highest occupied energy levels of atoms in order to achieve the electronic structure of a noble gas (Group 0). ONLY

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